Sciencemadness Discussion Board

Zinc sulfide thin films on glass

Freddybaby - 18-3-2011 at 16:35

Trying to deposit very thin films of ZnS on glass for gamma detector. This stuff does not mix well with much on my shelf.

Thought about combining with Sylgard silicone elastomere, similar to Sol gel but it's expensive and my needs are small.

Anyone have any ideas ??

Also, I wonder how much the microscope slide will attenuate the light level ? Perhaps a glass coverslip instead

[Edited on 19-3-2011 by Freddybaby]

redox - 18-3-2011 at 16:52

Does the zinc sulfide have to be strongly adhered to the glass surface? Or can it be loose?

Freddybaby - 18-3-2011 at 19:15

It should be bonded to the glass but even simple adhesion would be fine. A photo sensor will be on the opposite side and the entire assem bonded together.

The ZnS should be fairly protected I guess, it will be exposed to the atmosphere but the coating over the sulfide must be thin for sensitivity.

Ozone - 19-3-2011 at 07:01

"..must be thin for sensitivity."

Not so for gammas! A glass slide over the one with the ZnS secured with rubber bands would be fine, and would demonstrate little to no decrease in counting efficiency (aside from the fact the ZnS is a pretty crummy scintillator). You want the material to be even, but not so thick that your detector (photodiode, PMT, etc.) cannot see the pulses from the active side. Also, look up ZnS(Ag) (doped with Ag) which is a much more efficient material.



unionised - 20-3-2011 at 02:43

Would something like this help?

White Yeti - 4-8-2011 at 07:36

Do you have a furnace?
Zinc sulphide sublimes at ~1100C, you could deposit it onto a glass surface by heating some zinc sulphide under a piece of glass. The added bonus to this method is that any impurities are left behind or evaporated away under the intense heat. Alternatively, if you already have high purity zinc sulphide, you could melt some glass and mix some of it in, stir, extrude into a sheet and let cool.

Wizzard - 4-8-2011 at 12:11

Ungh, I don't know what happen to my last post... Apparently it was never sent.

I second the ZnS sublimation idea.

Encase a Ta/Moly boat in a small brick box, sealed with some clay. Fill with argon (recommended?), loosely seal the top with some material. Short some volts across the with some carbon terminals. Heat to red hot, replace the atmosphere (getting rid of zinc and sulfur), place your glass close above the boat, forming a loose seal over the top, and then heat the boat as hot as it will go.

ZnS melts at 1830*C, I think.

redox - 4-8-2011 at 14:07

How about sandwiching the powder in between two planes of glass, like microscope slides? I'm not very learned in nuclear chemistry (I prefer to stick to organic), but would the extra sheet of glass interfere with readings?

Just a thought.

White Yeti - 4-8-2011 at 15:23


Yes it would. Beta rays don't make it though a millimetre of aluminium and alpha rays are even easier to stop. The only way to get readings is to have a thin film of scintillator attached to a glass substrate, or to somehow embed the scintillator inside a very thin piece of glass.

Good thinking though.

redox - 4-8-2011 at 16:20

Oh. For some reason I thought this was a scintillator for gamma rays, which, of course, could penetrate.

White Yeti - 4-8-2011 at 17:34

Gamma rays would penetrate, but they wouldn't interact much with the zinc sulfide. Zinc sulfide, from what I understand, scintillates in the presence of alpha, beta and X radiation, not gamma. Freddybaby is probably trying to build a scintillation counter, but in order to detect gamma rays (specifically), different scintillator materials must be used. Besides, the decay of common radioisotopes results in the emission of alpha and beta particles (gamma radiation is negligible).

So the OP must have misunderstood something. Detecting gamma radiation is not a reliable way to measure radioactivity in rocks/ radium dials/ medical isotopes etc... Zinc sulfide only allows you to detect alpha and beta particles.